Bioaugmentation Potential Research Articles

Unveiling six novel bacterial strains for fipronil and thiobencarb biodegradation: efficacy, metabolic pathways, and bioaugmentation potential in paddy soil.

Soil bacteria offer a promising approach to bioremediate pesticide contamination in agricultural ecosystems. This study investigated the potential of bacteria isolated from rice paddy soil for bioremediating fipronil and thiobencarb, common agricultural pesticides. Bacterial isolates capable of degrading fipronil and thiobencarb were enriched in a mineral salt medium. A response surface methodology with a Box-Behnken design was utilized to optimize pesticide degradation with the isolated bacteria. Bioaugmentation tests were performed in paddy soils with varying conditions. Six strains, including single isolates and their mixture, efficiently degraded these pesticides at high concentrations (up to 800 µg/mL). Enterobacter sp., Brucella sp. (alone and combined), and a mixture of Stenotrophomonas sp., Bordetella sp., and Citrobacter sp. effectively degraded fipronil and thiobencarb, respectively. Notably, a single Pseudomonas sp. strain degraded a mixture of both pesticides. Optimal degradation conditions were identified as a slightly acidic pH (6-7), moderate pesticide concentrations (20-50 µg/mL), and a specific inoculum size. Bioaugmentation assays in real-world paddy soils (sterile/non-sterile, varying moisture) demonstrated that these bacteria significantly increased degradation rates (up to 14.15-fold for fipronil and 5.13-fold for thiobencarb). The study identifies these novel bacterial strains as promising tools for bioremediation and bioaugmentation strategies to tackle fipronil and thiobencarb contamination in paddy ecosystems.

Enhanced tetracycline removal in sequencing batch reactors by bioaugmentation using tetX-carrying strains: Efficiency and mechanisms

Tetracyclines antibiotics (TCs) pose notable environmental challenges due to their persistence in the effluent of wastewater treatment systems. Bioaugmentation offers a promising strategy for their removal, yet information is still very limited. This study aimed to assess the efficacy of bioaugmentation using wild-type (Sphingobacterium sp. WM1) and engineered tetX-carrying (PUC-tetX) strains for enhancing tetracycline (TC) removal in sequencing batch reactors (SBRs). Bioaugmentation mitigated TC's inhibitory effects on denitrification and phosphorus removal processes within SBR systems. Specifically, strain WM1 outperformed strain PUC-tetX in removing TC from sludge and maintained a longer viability. TC addition (500 μg/L, at an environmentally relevant concentration) and bioaugmentation did not significantly impact overall microbial community diversity. Notably, the introduction of these exogenous bacteria markedly increased the abundance of the tetX gene, correlating with the increase in TC degradation. Interestingly, MAGs associated with the Chloroflexi phylum in bioaugmented reactors showed the transfer of the tetX gene to autochthonous bacterial species, promoting TC removal capability. These findings underscored the potential of bioaugmentation to enhance antibiotic removal and provided insights into the dynamics of ARGs and tetX gene within activated sludge systems.

Unlocking the bioremediation potential of adapted Desulfovibrio desulfuricans in acidic low-temperature U-contaminated groundwater

Addressing the global challenge of uranium (U)-contaminated groundwater requires innovative bioremediation strategies. This study investigates Desulfovibrio desulfuricans, a neutrophilic and mesophilic sulfate-reducing bacteria (SRB) strain optimized for low-temperature (15 °C) and acidic (initial pH 4) conditions, to validate its bioaugmentation potential for uranium decontamination in groundwater. Our research aimed to assess its efficacy in treating U-contaminated groundwater and elucidate the optimal growth conditions for this strain in acidic and sulfate-enriched environments. We found that D. desulfuricans was phylogenetically distinct from the native microbial community in acidic U-contaminated groundwater, while it maintained appreciable activity in sulfate reduction under contaminated groundwater conditions after accumulation. Acid-tolerant D. desulfuricans removed 75.87 % of uranium and 30.64 % of sulfate from acidic U-contaminated groundwater (pH 4.0) at 15 °C within 14 days. Furthermore, we explored the optimal sulfate concentration for bacterial growth, which was found to be 2000 mg/L, and an elevated Fe2+ concentration from 100 to 1000 mg/L increasingly stimulated sulfate-reducing activity. These findings provide a novel insight into the application of neutrophilic and mesophilic SRB in bioremediation of acidic and low-temperature groundwater after accumulation and underscore the feasibility of bioremediation by using exogenously pure SRB.

Design and Implementation of a Biogas Pilot Plant for Bioaugmentation Strategies in a rural municipality

The transition towards renewable energy sources is imperative for achieving sustainability and mitigating climate change impacts. Among various renewable energies, biogas stands out for its dual role in waste management and energy production. This study introduces the design and implementation of a biogas pilot plant aimed at exploring bioaugmentation strategies to enhance biogas yield and quality. The pilot plant, located at Aras de los Olmos, features two independent 3.4m3 digesters, allowing for parallel comparison between standard anaerobic digestion and digestion with microbial enhancements. The plant is equipped with monitoring and control systems for precise regulation of environmental conditions, such as temperature, and for real-time measurement of biogas composition. Some initial experiments using a mix of agricultural wastes demonstrated the plant's capability to adapt to varied feedstock. Despite suboptimal temperature conditions, preliminary results indicated a high methane content, suggesting significant potential for bioaugmentation to improve biogas production efficiency. The study highlights the importance of controlled environmental conditions and introduces a novel bioaugmented digestion approach using selected microbial consortia. This research contributes to the broader goal of enhancing biogas technology's efficiency and sustainability, offering insights into the practical application of bioaugmentation in biogas production.

Bioaugmentation of manures by a tiamulin-degrading Sphingomonas as a means to alleviate environmental dispersal of antibiotic residues

Bioaugmentation of veterinary antibiotic (VA)-contaminated feces with VA-degrading bacteria, can reduce the VA-selective pressure on manure microorganisms toward antibiotic resistance during organic soil fertilization. We explored the efficiency of a Sphingomonas isolate, able to degrade tiamulin (TIA), as a bioaugmentation agent for removing TIA from pig manures fortified with TIA at two concentrations (5 and 50 µg g−1). Bioaugmentation efficiency was compared with stockpiling and anaerobic digestion. Bioaugmentation accelerated TIA dissipation (DT50 = 32.3 and 66.2 days) compared with anaerobic digestion (DT50 = 103 and 126.7 days) and stockpiling (DT50 = 95.38 and 113.8 days). Furthermore, we determined the impact of TIA on methane production and followed microbial succession during anaerobic digestion. The lower TIA concentration stimulated biomethanation, seemingly, through induction of the increase of Methanosarcina (from below detection at the TIA-free samples to 17.1% of relative abundance at the low in TIA content samples), commonly linked with aceticlastic biomethanation. Our findings highlight (i) the potential of bioaugmentation in treating VA-contaminated manures for mitigating the dispersal of VA residues in agricultural settings (ii) the high risk of contamination of agricultural soils by the use of TIA-contaminated manures that have been stockpiled or anaerobically digested before their use in agricultural settings.

Research Progress on Bioaugmentation Technology for Improving Traditional Chinese Fermented Seasonings

Chinese traditional fermented seasonings, essential to the culinary heritage of China, are produced through fermentation, resulting in a diverse range of unique flavors and aromas. The microorganisms involved in fermentation play significant roles in shaping the quality of these traditional fermented seasonings. The production of traditional fermented seasonings is affected by various biological and abiotic factors, presenting challenges concerning product quality and safety. This review investigates the impact of bioaugmentation technology on key Chinese traditional fermented seasonings, such as vinegar, soy sauce, sufu, doubanjiang, dajiang, and douchi. Additionally, the challenges and constraints linked to the implementation of bioaugmentation technology are discussed. The potential of bioaugmentation is highlighted by its ability to shorten the fermentation time, optimize raw material utilization, improve nutritional value, and enhance the quality parameters of these seasonings. This paper demonstrates an interesting convergence of traditional culinary heritage and contemporary technological advancements.

Adaptation strategies and functional transitions of microbial community in pyrene-contaminated soils promoted by lead with Pseudomonas veronii and its extracellular polymeric substances

Pyrene was designated as a remediation target in this study, and low contamination of lead (Pb) was set to induce heavy metal stress. Pseudomonas veronii and its extracellular polymeric substances (EPSs) were chosen for biofortification, with the aim of elucidating the structural, metabolic, and functional responses of soil microbial communities. Community analysis of soil microorganisms using high-throughput sequencing showed that the co-addition of P. veronii and EPSs resulted in an increase in relative abundance of phyla associated with pyrene degradation, and formed a symbiotic system dominated by Firmicutes and Proteobacteria, which involved in pyrene metabolism. Co-occurrence network analysis revealed that the module containing P. veronii was the only one exhibiting a positive correlation between bacterial abundance and pyrene removal, indicating the potential of bioaugmentation in enriching functional taxa. Biofortification also enhanced the abundance of functional gene linked to EPS production (biofilm formation-Pseudomonas aeruginosa) and pyrene degradation. Furthermore, 17 potential functional bacteria were screened out using random forest algorithm. Lead contamination further promoted the growth of Proteobacteria, intensified cooperative associations among bacteria, and increased the abundance of bacteria with positive correlation with pyrene degradation. The results offer novel perspectives on alterations in microbial communities resulting from the synergistic impact of heavy metal stress and biofortification.

Culturable Bacterial Endophytes of Wild White Poplar (Populus alba L.) Roots: A First Insight into Their Plant Growth-Stimulating and Bioaugmentation Potential.

The white poplar (Populus alba L.) has good potential for a green economy and phytoremediation. Bioaugmentation using endophytic bacteria can be considered as a safe strategy to increase poplar productivity and its resistance to toxic urban conditions. The aim of our work was to find the most promising strains of bacterial endophytes to enhance the growth of white poplar in unfavorable environmental conditions. To this end, for the first time, we performed whole-genome sequencing of 14 bacterial strains isolated from the tissues of the roots of white poplar in different geographical locations. We then performed a bioinformatics search to identify genes that may be useful for poplar growth and resistance to environmental pollutants and pathogens. Almost all endophytic bacteria obtained from white poplar roots are new strains of known species belonging to the genera Bacillus, Corynebacterium, Kocuria, Micrococcus, Peribacillus, Pseudomonas, and Staphylococcus. The genomes of the strains contain genes involved in the enhanced metabolism of nitrogen, phosphorus, and metals, the synthesis of valuable secondary metabolites, and the detoxification of heavy metals and organic pollutants. All the strains are able to grow on media without nitrogen sources, which indicates their ability to fix atmospheric nitrogen. It is concluded that the strains belonging to the genus Pseudomonas and bacteria of the species Kocuria rosea have the best poplar growth-stimulating and bioaugmentation potential, and the roots of white poplar are a valuable source for isolation of endophytic bacteria for possible application in ecobiotechnology.

Efficient atrazine removal in bioaugmentation constructed wetland: Insight from stable isotope fractionation analysis

Constructed wetlands (CW) provides a sustainable approach to remove pesticides from agricultural or urban runoff, while the low efficiency of the herbicide atrazine remains a challenge. Focused on improving atrazine removal in CW, a bioaugmentation strategy was implemented using the mixed culture of atrazine-degrading bacteria. The results shown a significant increase in atrazine removal from 26.2 ± 6.9% to 60.9 ± 8.7–90.6 ± 4.1% during the bioaugmentation phases. To investigate in-situ degradation processes of atrazine, compound-specific stable isotope analysis (CSIA) was conducted. The carbon and nitrogen isotope fractionation pattern revealed atrazine was primarily degraded via a hydrolysis pathway mediated by microorganisms. The biodegradation extent of atrazine calculated from δ13C signatures suggested that 90% of atrazine was removed via the hydrolysis pathway, with only a small portion being removed abiotically. This was additionally supported by an increase in microbial diversity and the abundance of specific bacteria (such as Rhizobium sp. and Pseudomonas sp.) capable of degrading atrazine. Altogether, this study demonstrated the effectiveness of atrazine-degrading mixed culture and its feasibility on bioaugmentation atrazine removal in CW. This work highlights the potential of bioaugmentation in sustainable pesticide removal approaches and CSIA can contribute to an understanding of in-situ pesticide transformation processes in wetland systems.

A Bioaugmentation Approach for Efficient Total Nitrogen Reduction in Landfill Leachate

In this study, the focus was on assessing the efficacy of Bioaugmentation in addressing Total Nitrogen (TN) levels in leachate from one of South Korea’s largest waste landfills. The utilization of proprietary bioaugmentation technology led to a remarkable 89% reduction in Total Nitrogen levels within a mere three weeks of implementation at the site. The significant outcome of this reduction not only ensured compliance with stringent Total Nitrogen discharge standards but also brought about the added advantage of eliminating the need for certain chemicals in the leachate treatment process. This dual benefit highlights the practical and sustainable nature of Bioaugmentation as a solution for Total Nitrogen reduction in Landfill Leachate. The findings from this study contribute valuable insights into the potential of Bioaugmentation as a cost-effective and efficient strategy. The ability to expedite the reduction of Total Nitrogen levels in landfill leachate not only addresses environmental concerns but also holds promise for streamlining waste management practices on a larger scale. As we move forward, such innovative approaches could play a crucial role in shaping more sustainable and eco-friendly solutions for waste treatment in landfills.

Bioaugmentation Potential Investigation Using a Phenol Affinity Analysis of Three Acinetobacter Strains in a Multi-Carbon-Source Condition

Bioaugmentation potential and phenol substrate affinity in a multi-carbon-source condition for three Acinetobacter strains (Acinetobacter towneri CFII-87, Acinetobacter johnsonii CFII-99A and Acinetobacter sp. CFII-98) were demonstrated. First, the phenol biodegradation ability of the strains was analyzed in batch experiments with phenol as the sole carbon source. All strains degraded phenol at 100 and 500 mg·L−1 initial concentrations; the maximum specific growth rates were 0.59 and 0.30 d−1 for A. towneri CFII-87, 0.50 and 0.20 d−1 for A. johnsonii CFII-99A, and 0.64 and 0.29 d−1 for A. sp. CFII-98, respectively. For the two tested phenol concentrations, no lag phase was observed for the A. towneri CFII-87 strain, A. sp. CFII-98 presented 4 h and 8 h lag phase, while A. johnsonii CFII-99A presented 3 h and 12 h lag phases. Phenol carbon source dependency of the strains was tested in a multi-carbon-source condition (on phenol-rich synthetic wastewater), both for individual strains and for a consortium prepared as an equal mixture of the three strains. The strains A. towneri CFII-87 and A. sp. CFII-98 and the consortia degraded phenol in 16 h while there was no other significant carbon source consumption during the 48 h trial, as shown by the constant non-phenolic residual chemical oxygen demand (COD) and volatile suspended solids (VSS) concentration after the depletion of phenol. The strain A. johnsonii CFII-99A, however, consumed phenol within 24 h and a further decrease in non-phenolic COD and increase in biomass was also observed upon the depletion of phenol. The highest specific phenol removal rate of 282.11 mg phenol·g VSS∙h−1 was observed in the case of the strain A. towneri CFII-87, followed by A. sp. CFII-98, the consortium and A. johnsonii CFII-99A with 178.84, 146.76 and 141.01 mg phenol·g VSS∙h−1, respectively. Two bacterial strains (A. towneri CFII-87, A. sp. CFII-98) presented a strong affinity to phenol, utilizing it as a primary carbon source, and thus, their use in the bioaugmentation of wastewater bioreactors indicated the viable potential to increase the phenol removal rate of these systems.

Bioaugmentation of a structural extracellular polymeric substances (EPS) producer to improve activated sludge bioflocculation: lessons learned

Abstract Structural extracellular polymeric substances (EPS) contribute to the bioflocculation performance of activated sludge systems. This research investigates the potential of bioaugmentation of a structural EPS producer, Azoarcus communis, as a bioflocculation improvement or remediation approach. An antibiotic-resistant and fluorescent protein-producing mutant was constructed to monitor the survival, persistence, and location of the augmented strain in the membrane bioreactor. Preliminary batch tests against a kaolin clay model system and deflocculated sludge revealed the flocculation potential of this strain. Morphological image analysis and fluorescence microscopy suggest that most of the bacteria augmented in suspension were initially attached to the sludge flocs with, however, only a limited fraction getting incorporated within the activated sludge floc biomass. This limited bioaugmentation prevented assessing its impact on bioflocculation and might be explained by metazoan and protozoan grazing, together with competition with indigenous organisms and sub-optimal growth conditions in the reactor for the engineered strain.

Bioaugmentation potential of inoculum derived from anaerobic digestion feedstock for enhanced methane production using water hyacinth

The utilisation of water hyacinth for production of biogas is considered to be a solution to both its control and the global renewable energy challenge. In this instance, an investigation was conducted to evaluate the potential of water hyacinth inoculum to enhance methane production during anaerobic digestion (AD). Chopped whole water hyacinth (10% (w/v)) was digested to prepare an inoculum consisting mainly of water hyacinth indigenous microbes. The inoculum was incorporated in the AD of freshly chopped whole water hyacinth to set up different ratios of water hyacinth inoculum and water hyacinth mixture with appropriate controls. The results of batch tests with water hyacinth inoculum showed a maximal cumulative volume of 211.67 ml of methane after 29 days of AD as opposed to 88.6 ml of methane generated from the control treatment without inoculum. In addition to improving methane production, inclusion of water hyacinth inoculum reduced the electrical conductivity (EC) values of the resultant digestate, and, amplification of nifH and phoD genes in the digestate accentuates it as a potential soil ameliorant. This study provides an insight into the potential of water hyacinth inoculum to enhance methane production and contribute to the feasibility of the digestate as a soil fertility enhancer.

Triisobutyl phosphate biodegradation by enriched activated sludge consortia: Degradation mechanism and bioaugmentation potential

This study investigated the ability of activated sludge (AS) to biodegrade triisobutyl phosphate (TiBP) after acclimation in an AS bioreactor by adding 50 mg/L TiBP. The bioreactor significantly increased the biotransformation rate of TiBP (2.15–12.7 d−1) over two months of acclimation. Seven transformation products (TPs) of TiBP were identified by high-resolution mass spectrometry, and hydrolysis, hydroxylation and dehydrogenation were the major biodegradation pathways of TiBP. TiBP degradation solutions at 0, 3, 7, and 10 h showed significantly toxic effects on zebrafish embryos, while the toxicity of TiBP degradation solutions at 24 h significantly decreased. Pseudomonas was inferred to be a specific bacterial population in the TiBP metabolic microbial consortium (TMMC) that degrades TiBP (p < 0.001). When TMMC (0.5, 1, and 2 gss/L) was introduced into AS, the TiBP biotransformation rates (1.97, 2.05, and 2.26 d−1 at 1.0 mg/L TiBP, and 0.09, 0.11, and 0.83 d−1 at 30.0 mg/L TiBP) were significantly enhanced compared to the control (0.31 and 0.07 d−1) without TMMC inoculation. In general, this study provides new insights into the key species populations that accelerate TiBP degradation and promote the development of TiBP reduction biotechnology in WWTPs.

Assessing quinoline removal performances of an aerobic continuous moving bed biofilm reactor (MBBR) bioaugmented with Pseudomonas citronellolis LV1

This study evaluated the bioaugmentation potential of a quinoline-degrading strain Pseudomonas citronellolis LV1 inoculation into activated sludge for treating quinoline wastewater, and results indicated the inoculation of LV1 in aerobic continuous MBBR could substantially improve the quinoline removal performance with an improved removal efficiency of 34% averagely when quinoline was used as the sole carbon and nitrogen source. Additionally, efficient removal of quinoline in enhanced MBBR occurred at the influent pH of 7.0–8.0, hydraulic retention time (HRT) of 24–28 h and influent quinoline concentration of 100–700 mg·L−1. High-throughput sequencing analysis indicated that bioaugmentation could increase microbial diversity and shape the microbial community structure. Although the inoculant LV1 did not remain its dominance in stage III, bioaugmentation indeed induced the formation of effective microbial community, and the indigenous microbes including Flavobacterium, Pseudoxanthomonas, Pseudomonas, Vermamoeba, Dyadobacter and Sphingomonas might play the key role in quinoline removal. According to the PICRUSt, the enhanced genes encoding aromatic ring-cleavage enzyme, especially for N-heterocyclic ring-cleavage enzymes, could lead to the improved removal performance of quinoline in bioaugmentation stage. Moreover, the enhanced MBBR treated well actual coking wastewater, as indicated by high removal performance of quinoline, phenol and COD.

Nitrogen removal intensification of aerobic granular sludge through bioaugmentation with “heterotrophic nitrification-aerobic denitrification” consortium during petroleum wastewater treatment

The bioaugmentation potential of aerobic granular sludge (AGS) was investigated using heterotrophic nitrification-aerobic denitrification (HN-AD) bacterial consortium to improve nitrogen removal during petroleum wastewater treatment. An efficient HN-AD consortium was constructed by mixing Pseudomonas mendocina K0, Brucella sp. K1, Pseudomonas putida T4 and Paracoccus sp. T9. AGS bioaugmented by immobilized HN-AD consortium enhanced nitrogen removal, which showed NH4+-N and TN removal efficiency of 92.4% and 79.8%, respectively. The immobilized consortium addition facilitated larger AGS formation, while granules > 2.0 mm accounted for 16.7% higher than that of control (6.7%). Further, the abundance of napA gene was 4-times higher in the bioaugmented AGS as compared to the control, which demonstrated the long-term stability of HN-AD consortium in the bioreactor. The bioaugmented AGS also showed a higher abundance of xenobiotics biodegradation and nitrogen metabolism. These results highlight that bioaugmentation of AGS technology could be effectively used for enhanced denitrification of petroleum wastewater.

Natural bioaugmentation enhances the application potential of biochar for Cd remediation

As the reuse of agricultural and forestry waste, leaf biochar can remove heavy metals from the environment, avoid secondary pollution while creating economic and environmental benefits for society. Our research presents an innovative approach to preparing efficient adsorbents for the first time using natural bioaugmentation (decay) pretreatment of fallen leaves biomass followed by pyrolysis to biochar. Compared with the pristine biochar derived from leaf (BC), the natural bioaugmentation biochar (NBC) characterization showed that the enhancement of microstructure increased the specific surface area, the change of surface composition increased the oxygen-containing functional groups and active adsorption sites, and the increase of porosity improved the mass transfer rate, resulting in a 2-fold increase of Cd(II) fixation capacity. Langmuir and pseudo-second-order models demonstrated that Cd(II) adhered to the NBC core sites through chemical reaction sites by a spontaneous process. The release of nutrients and changes in soil pH after NBC addition to contaminated soil enhanced the stability of the ecosystem and promoted plant growth. This study illustrates for the first time the great potential of natural bioaugmentation (decay) leaf-derived biochar for heavy metal adsorption and provides a new idea to explore the reuse of cellulose waste resources.

Bioaugmentation potential of a cold-adapted and nitrate-reducing fungus to enhance nitrate removal in woodchip bioreactors

Woodchip bioreactors are a promising approach to remove nitrate from agricultural drainage systems; however, their low removal efficiency at cold temperatures remains a significant challenge. Here we analyzed the efficacy of fungal inoculation to enhance nitrate removal in woodchip bioreactor microcosms under cold conditions. Among the cold-adapted, nitrate-reducing, and cellulose-degrading fungi previously isolated from soil, we identified Linnemannia hyaline strain SCG-10 as the fastest nitrate reducer. Inoculation of this fungal strain enhanced the rates of nitrate reduction, N2 production, and dissolved organic carbon production in woodchip bioreactor microcosms at 5 °C. Production of N2O was minor (<1%) in this study most likely due to the enhanced activity of N2O reducers by labile carbon. Quantitative PCR for nitrogen cycle-related genes showed the active transcription of both fungal and bacterial denitrification genes. These results suggest that inoculating cold-adapted, nitrate-reducing, and cellulose-degrading fungi is a promising approach to remove nitrate from agricultural fields under cold conditions.

Methyl Orange Biodegradation by Immobilized Consortium Microspheres: Experimental Design Approach, Toxicity Study and Bioaugmentation Potential.

Simple SummaryAn efficient immobilized bacterial consortium of Raoultella planticola, Ochrobactrum thiophenivorans, Bacillus flexus, and Staphylococcus xylosus was used to degrade MO under high salinity conditions. The biodegradation efficiency was confirmed by UV−visible spectrophotometric analysis, FTIR, and the assaying of degradative enzymes. The cytotoxicity of such metabolic byproducts was evaluated on two human normal cell lines. In addition, the immobilized consortium showed the synergistic interaction between immobilized consortium and indigenous microorganism for degrading MO in artificially contaminated agricultural and industrial effluents.Methyl orange (MO) is categorized among the recalcitrant and refractory xenobiotics, representing a significant burden in the ecosystem. To clean-up the surrounding environment, advances in microbial degradation have been made. The main objective of this study was to investigate the extent to which an autochthonous consortium immobilized in alginate beads can promote an efficient biodegradation of MO. By employing response surface methodology (RSM), a parametric model explained the interaction of immobilized consortium (Raoultella planticola, Ochrobactrum thiophenivorans, Bacillus flexus and Staphylococcus xylosus) to assimilate 200 mg/L of MO in the presence of 40 g/L of NaCl within 120 h. Physicochemical analysis, including UV-Vis spectroscopy and FTIR, and monitoring of the degrading enzymes (azoreductase, DCIP reductase, NADH reductase, laccase, LiP, MnP, nitrate reductase and tyrosinase) were used to evaluate MO degradation. In addition, the toxicity of MO-degradation products was investigated by means of phytotoxicity and cytotoxicity. Chlorella vulgaris retained its photosynthetic performance (>78%), as shown by the contents of chlorophyll-a, chlorophyll-b and carotenoids. The viability of normal lung and kidney cell lines was recorded to be 90.63% and 99.23%, respectively, upon exposure to MO-metabolic outcomes. These results reflect the non-toxicity of treated samples, implying their utilization in ferti-irrigation applications and industrial cooling systems. Moreover, the immobilized consortium was employed in the bioremediation of MO from artificially contaminated agricultural and industrial effluents, in augmented and non-augmented systems. Bacterial consortium remediated MO by 155 and 128.5 mg/L in augmented systems of agricultural and industrial effluents, respectively, within 144 h, revealing its mutual synergistic interaction with both indigenous microbiotas despite differences in their chemical, physical and microbial contents. These promising results encourage the application of immobilized consortium in bioaugmentation studies using different resources.

Rapid Metabolism of 1,4-Dioxane to below Health Advisory Levels by Thiamine-Amended Rhodococcus ruber Strain 219

Bioremediation is a promising treatment technology for 1,4-dioxane-contaminated groundwater. However, metabolic dioxane-degrading bacteria identified to date are limited by their slow kinetics and inability to sustain growth at low dioxane concentrations (<100 μg/L). Furthermore, strains may underperform because of missing growth factors, such as amino acids or vitamins. In this work, we reevaluate Rhodococcus ruber strain 219 as a dioxane-degrading strain with bioaugmentation potential. We report rapid growth and metabolic dioxane degradation by R. ruber 219 when supplemented with thiamine (vitamin B1). We also discern that the strain lacks a complete de novo thiamine synthesis pathway, indicating that R. ruber 219 is a probable thiamine auxotroph. However, when supplemented with thiamine, the strain’s Monod kinetics (Ks = 0.015 ± 0.03 μg/L) and exceedingly low Smin (0.49 ± 1.16 μg/L) suggest this strain can maintain growth at very low dioxane concentrations (<100 μg/L). Accordingly, we demonstrate that thiamine-grown R. ruber 219 sustains degradation of dilute dioxane (<100 μg/L) to below health advisory levels. This is the first study to report sustained metabolic dioxane biodegradation to below health advisory levels of 0.35 μg/L. Overall, our findings solidify R. ruber 219 as a promising candidate for bioremediation of dioxane-contaminated groundwater.